462 THE ANOMADURES
as gnawing and excavating tools as well as for the purposes of
alimentation; for it allows of substances being gnawed away
without the products of the chisel-like action being taken into
the hinder cavity of the mouth. The Rodents have for the most
part a simple stomach of normal form; but in a few this is
complicated by a marked constriction, which divides the cardiac
from the pyloric portions. The Hamster, for example, is thus
characterised. In all the members of the order, with the excep-
tion of the Dormice and some allied forms, the caecum is large
and often sacculated. In some forms (e.g. A.rvicola, My odes,
Cuniculus} the large intestine is coiled upon itself in a spiral way
---a state of affairs strongly suggestive of Ruminants.
The Rodents are primarily divisible into two great groups, the
Simplicidentata and the Duplicidentata, characterised mainly by
the upper incisor teeth. In the former there is but one pair of
these teeth; in the latter a second smaller pair lie behind the
SUB-OKDEK 1. SIMPLICIDENTATA.
SECTION 1. SCTUKOMORPHA.
The Anomaluri are separated by Thomas and others from this
section as an equal section,, while by Tullberg they are grouped
Fain. 1. Anomalurxdae.—The genus A,no7nalurus suggests at
first sight the Flying Squirrels of Asia, Pteromys. It is, how-
ever, an entirely African genus, and is to be distinguished from
the Asiatic Rodents by a series of scales at the root of the tail,
imbricated, keeled, and forming possibly a " climbing organ,"
This character serves also to distinguish the present genus from
Sciuroyterus. The cartilage, moreover, which supports the
patagium springs from the elbow. There are four molars in each
half of each jaw. The eyes and ears are large. There are five
fingers and toes, but the thumb is small, though provided with
a naiL The sternum lias seven joints, and nine ribs reach it.
The clavicle is strong. Huet, who has recently monographed the
genus,1 allows six species. The species vary in size.
1 "Observations sur le genre <dnoma2urus," JtVbuv. Arch* Mi&s, (2), vi. 1583,